Various volatile organic compounds may enter into the environment water bodies such as surface water, ground water, seawater etc. and the production and living water in many ways such as by means of emission, leakage or diffusion etc. The volatile organic compounds will impose unfavorable influence on or potential threat to environment, ecology, safety and health etc. depending on their different properties. Various organic compounds such as aromatic hydrocarbon, aliphatic hydrocarbon and halogenated hydrocarbon are not easily decomposed due to their stable chemical properties. They will penetrate into groundwater aquifers and cause serious destruction to the environment. Long-term contact with such organic compounds will result in human chronic poisoning, induce cancer and also have a direct influence on the reproductive system and nervous system. Therefore, monitoring of the volatile organic pollutants in water gets increasingly important in environment analysis work. The causes for water pollution includes improper treatment of industrial waste water, improper treatment of household garbage, leakage events of petroleum chemical plants and leakage events of ships at sea. As for some leakage events, urgent measures must be taken to cut off the spread of pollution as quickly as possible. Therefore, it is extremely important to quickly determine the pollution situations of the water body. The conventional manner by sampling polluted water source and bringing the sample back to a laboratory for detection obviously cannot deal with various sudden events, and some portable detection instruments usually have disadvantages such as undesirable accuracy of measurement result, high cost of the instrument and inconvenient for carrying.
The difficulty in detecting volatile organic compound (VOC) in water body lies in in-situ sampling and quick analysis. The conventional sampling manner is generally as follows, i.e. after sampling in a vessel, sending it to a laboratory for extraction (e.g., as disclosed in US patent application US2011/094105 A1), enrichment (e.g., as disclosed in US patent application US2001/0003426A1) or purging-and-trapping methods and the like. Obviously, these methods cannot meet the requirements for in-situ test, and the components of the water body inevitably change to some extent due to a longer time interval delayed from sampling to testing. In addition, the subsequent processes such as extraction, enrichment and purging-and-trapping etc. are complicated, quite time consuming and cannot completely reflect/indicate the actual water sample components. Collecting the volatile gas in water by using a headspace method is obviously superior to the situation by using the above sampling method. The U.S. Pat. No. 5,773,713 disclosed the use of a detection method in which a polymer membrane is placed in the detected water sample, VOCs in the water permeate or diffuse through the polymer membrane and are brought out by a dilution gas stream for detection. The U.S. Pat. No. 5,448,922 discloses a gas permeation system which also uses a gas permeation membrane. The method of using a membrane for separation is disadvantageous in that flow of the gas depends on properties of the membrane to a great extent, and is substantially affected by the material, length and cross-sectional area of the membrane and greatly affected by the pressure of the system. Therefore, the reliability is not so high and the structure is so complicated. It can be seen that up to date there is no such a device for efficiently, quickly, portably and reliably in-situ detecting the volatile organic pollutants in water.